plunged Monday after
chose Trend's antivirus software for its Hotmail Web email service.
Trend Micro will provide automatic antivirus scanning for Hotmail's 187 million email accounts. The contract is a coup for Trend Micro and a black eye for McAfee, which had previously provided virus protection for the service.
No immediate reason for the switch was offered by the companies involved.
Trend Micro rose $3.91, or 7.8%, to $54.39 in early trading Monday, while McAfee fell $2.64, or 9.1%, to $26.31.